Mixing species like that is generally frowned upon, and with good reason. I don't know anything about Degus, but I'm willing to bet that their nutritional requirements are quite different from those of chinchillas. I would get a neutered male chinchilla, and $100 isn't that much to spend on an animal, so your husband can deal. :P

Most people wouldn't want to fathom how much the Indigo Snake I'm getting for my man is going to cost, even without the setup.